By the mid-1970s, when cancer epidemiologists began to convince politicians and the public that many cancers were caused by what Peto and Doll had called the “gross aspects of diet,” rather than “ingestion of traces of powerful carcinogens or precarcinogens,” the focus was almost exclusively on fat, fiber, and red meat, or smoked-or salt-cured meat, as well as the possibly protective nature of vitamins, vegetables, and fruits. The low incidence of cancer in vegetarians and Seventh-day Adventists was often cited as evidence that meat is carcinogenic and that green vegetables and fruit are protective. (Although the incidence of colon cancer, for instance, among Seventh-day Adventists was no lower than among Mormons, described by Doll and his colleague Bruce Armstrong as “among the biggest beefeaters in the United States.”) For the next twenty years, conferences, textbooks, and expert reports on nutrition and cancer continued to focus exclusively on these factors, although now aided by the advances in molecular biology.

By the end of the 1990s, clinical trials and large-scale prospective studies had demonstrated that the dietary fat and fiber hypotheses of cancer were almost assuredly wrong, and similar investigations had repeatedly failed to confirm that red meat played any role.*62 Meanwhile, cancer researchers had failed to identify any diet-related carcinogens or mutagens that could account for any of the major cancers. But cancer epidemiologists made little attempt to derive alternative explanations for those 10 to 70 percent of diet-induced cancers, other than to suggest that overnutrition, physical inactivity, and obesity perhaps played a role.

Throughout these decades, refined carbohydrates and sugars received little or no attention in discussions of cancer causation. Peter Cleave had suggested in The Saccharine Disease that the refining of carbohydrates might be involved in colon cancer. John Yudkin had noted that the five nations with the highest breast-cancer mortality in women in the late 1970s (in descending order: the United Kingdom, the Netherlands, Ireland, Denmark, and Canada) had the highest sugar consumption (in descending order: the United Kingdom, the Netherlands, Ireland, Canada, and Denmark), and those with the lowest mortality rates (Japan, Yugoslavia, Portugal, Spain, and Italy) had the lowest sugar consumption (Japan, Portugal, Spain, Yugoslavia, and Italy). But in 1989, when the National Academy of Sciences published its 750-page report on Diet and Health, the authors spent only a single page evaluating the proposition that carbohydrates might cause cancer. “There is little epidemiologic evidence to support a role for carbohydrates per se in the etiology of cancer,” they noted. They did add two caveats. One was that “no definitive conclusion is justified…because carbohydrates have often been reported in epidemiologic studies only as a component of total energy and not analyzed separately.” The other was that Richard Doll and Bruce Armstrong had found sugar intake in international comparisons to be “positively correlated with both the incidence of and mortality from” colon, rectal, breast, ovarian, prostate, kidney, nervous-system, and testicular cancer, and that “other investigators have produced similar findings.”